Method and apparatus for producing radially oriented ring magnet

ABSTRACT

The present invention provides a method and an apparatus for producing radially oriented ring magnet. The problem it solved is to uniformly orient the magnet powder in the process of producing, and also to get relatively large oriented magnetic field strength, so as to increase the performance and uniformity of the radial ring. The method of forming a radially oriented ring magnet, is to position magnetic powder into a ring mold, using an oriented magnetic field to orient the magnetic powder in the ring mold along the radius or diameter direction, wherein the oriented magnetic field is distributed discretely 360° around the ring mold, and during the forming process the oriented magnetic field and the magnetic powder have relative rotation. The apparatus comprises a ring mold cavity positioned in an oriented magnetic field, wherein the oriented magnetic field is distributed discretely 360° around the ring mold, and the apparatus comprises a component fot the oriented magnetic field and the magnetic powder to rotate relatively. Because the magnetic field is the same field in 360°, the orienting of the magnetic powder is more complete, the orientation in different directions is more unified.

BACKGROUND OF THE PRESENT INVENTION

1. Field of Invention

The present invention relates to a method and an apparatus for producing radially oriented ring magnet, and more particularly for the orientation along the radius or diameter of the ring magnet.

2. Description of Related Arts

Radially oriented ring magnet (also called radial ring or radially oriented ring) is widely used in the electric field. The biggest technical difficulty of fabricating the radial ring is to apply radial orienting to the powder body during the forming stage. Currently there are two major methods of orienting in this industry: the first is the sectional orienting method which separates the ring into several sections, and introduces each section into the magnet field individually. The disadvantage of this method is that the orientation is not uniform, some portion is higher, and some portion is lower. Not uniformed orientation would not only seriously affect the overall magnetic property of the magnet ring, but due to different level of orientation has different shrinkage in the sintering process and (or) heating treatment, it will lead to radial ring cracking or deformation, so as to reduce the performance, lower the production yield, and increase the cost. The second is the squeezed magnetic field orienting method, the method is to adjust the current direction of the two coils to generate a same pole (N pole or S pole) magnetic field between the terminals of the two coils, then to squeeze the same pole magnetic field into the inner cavity of the radial ring mold and to form a radial magnetic field through a magnetic conductive device. The disadvantage is when the inner diameter is small, the oriented magnetic field strength will reduce largely and will cause the magnetic powder orienting insufficiently (the first method has the same problem). In addition, when the height of the radial ring is high, the oriented magnetic field strength will reduce and the uniformity will be affected as well, this will fail the request of performance and uniformity.

SUMMARY OF THE PRESENT INVENTION

The present invention provides a method and an apparatus for producing radially oriented ring magnet. The problem it solved is to uniformly orient the magnet powder in the process of producing, and also to get relatively large oriented magnetic field strength even if the inner diameter of the magnet ring is too small, or the height of the magnetic ring is too high, so as to increase the performance and uniformity of the radial ring.

The present invention provides the following method: a method of forming a radially oriented ring magnet, is to position magnetic powder into a ring mold, using an oriented magnetic field to orient the magnetic powder in the ring mold along the radius or diameter direction, wherein the oriented magnetic field is distributed discretely 360° around the ring mold, and during the forming process the oriented magnetic field and the magnetic powder have relative rotation.

A method of forming a radially oriented ring magnet, comprises the steps of:

(a) applying a relatively small pressure onto the magnetic powder in the cavity of the mold to reduce the volume of the magnetic powder to 5% to 40%;

(b) introducing magnetic field to the pole of the oriented magnetic field, rotating the magnetic powder in the mold relating to the oriented magnetic field until the magnetic powder is totally magnetized;

(c) reducing the magnetic field strength of the oriented magnetic field until zero during rotating;

(d) applying more pressure on the magnetic powder until predetermined level; and

(e) applying reverse magnetic field to the radial ring bodyware for demagnetization, receiving radial ring bodyware.

An apparatus for forming radially oriented ring magnet comprises a ring mold cavity positioned in an oriented magnetic field, wherein the oriented magnetic field is distributed discretely 360° around the ring mold, and the apparatus comprises a component fot the oriented magnetic field and the magnetic powder to rotate relatively.

The oriented magnetic field of the present invention is a flake parallel magnetic field or near parallel magnetic field.

The width of the oriented magnetic field of the present invention along the diameter of the radial ring mold cavity is less than the inner diameter of the mold cavity.

The width of the oriented magnetic field of the present invention along the diameter of the radial ring mold cavity is less than the one fifth of the inner diameter of the mold cavity.

The inner pole of the oriented magnetic field is located in the center of the ring mold cavity, and the outer pole of the oriented magnetic field is located on the outside of the ring mold cavity. The magnetic conductive plate is located inside the outer pole to form a strong magnetic field between the inner pole and the magnetic conductive plate.

The present invention comprises more than one set of inner pole and magnetic conductive plate.

In the presenting invention, the mold cavity and the inner pole of the oriented magnetic field is fixed, the outer pole and the magnetic conductive plate of the oriented magnetic field are connected with the rotation driver; or the outer pole and the magnetic conductive plate are fixed, the mold cavity and the inner pole are connected with the rotation driver.

The first outer pole and the second outer pole of the oriented magnetic field of the present invention are positioned at the outside of the ring mold cavity facing to each other. A magnetic conductive core is located at the center of the ring mold cavity. The magnetic conductive core forms two strong magnetic fields respectively between the magnetic conductive core and the first outer pole, and between the magnetic conductive core and the second outer pole.

The mold cavity and the magnetic conductive core are fixed, the first outer pole and the second outer pole of the oriented magnetic field are connected with the rotation driver; or the first outer pole and the second outer pole are fixed, the mold cavity and the magnetic conductive core are connected with the rotation driver.

In the present invention, the first pole and the second pole have more than one pair.

In the present invention, the number of the first pole and the second pole is odd.

Comparing with the conventional technique, in the present invention, the oriented magnetic field is distributed discretely 360° around the ring magnet, and during the forming process the oriented magnetic field and the magnetic powder have relative rotation. Because the magnetic field is the same field in 360°, the orienting of the magnetic powder is more complete, the orientation in different directions is more unified. This invention can be used in producing sintering radial ring magnet, adhesion radial ring magnet, and injection radial ring magnet.

These and other objectives, features, and advantages of the present invention will become apparent from the following detailed description, the accompanying drawings, and the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of one embodiment of the present invention illustrating the inner pole—outer pole (1) orientation method.

FIG. 2 is a perspective view of one embodiment of the present invention illustrating the inner pole—outer pole (2) orientation method.

FIG. 3 is a perspective view of one embodiment of the present invention illustrating the outer pole—outer pole orientation method.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to the drawings of the present invention, the numbers indicate: 1. inner pole (can also acts a mold core if the hardness of the magnetic conductive material is large); 2. mold cavity; 3. nonmagnetic mold; 4. magnetic conductive plate; 5. outer pole; 6. magnetic field; 7. the first outer pole; 8. the second outer pole; 9. magnetic conductive core (can also acts a mold core if the hardness of the magnetic conductive material is large).

In the method of forming radial oriented ring magnet of the present invention, the selected oriented magnetic field is not distributed all around the mold cavity in 360°, but is limited in a portion of the mold cavity. The width in the diameter direction of the mold cavity is less than the inner diameter of the mold cavity, the optimum width is the one fifth of the inner diameter of the mold cavity. The 360° orientation of the magnetic powder is realized by continuously rotating the mold cavity and the magnetic powder inside the mold cavity relating to the oriented magnetic field for plural of rounds, instead of applying a 360° or near 360° radial oriented magnetic field as the conventional method. The oriented magnetic field is using flake parallel magnetic field or near flake parallel magnetic field instead of the ring radial magnetic field. The parallel magnetic field is a well developed technique which is easy to realizand can provide strong magnetic field. On the contrary, it is difficult for a ring magnetic field to provide a strong magnetic field. The present invention is using a mature technique to achieve the effect which needs non- mature technique to achieve.

The present invention has two preferred embodiment to realize: (1) the inner pole—outer pole method; and (2) the outer pole—outer pole method.

Referring to FIG. 1, after introducing the two poles (N and S) of a magnetic field generated by an electromagnet or a permanent magnet into the inner pole 1 and the outer pole 5 though a magnetic conductive component respectively, a strong magnetic field 6 will be formed between the inner pole 1 and the magnetic conductive plate 4 in the inside of the outer pole 5. If the mold cavity 2 is filled with magnetic powder, the magnetic powder in the magnetic field 6 will be sufficiently magnetized and oriented. If the first method is used, the nonmagnetic mold 3, mold cavity 2, and inner pole 1 are fixed on the platform of the apparatus and are relatively static. The outer pole 5 and magnetic conductive plate 4 are connected with the rotation driver to rotate around the nonmagnetic mold 3, mold cavity 2, and inner pole 1. If the second method is used, outer pole 5 and magnetic conductive plate 4 are fixed on the platform of the apparatus and are relatively static, nonmagnetic mold 3, mold cavity 2, and inner pole 1 are connected with the rotation driver to rotate to magnetize and radially orient all the magnetic powder in the mold cavity 2. At the same time of magnetization and orientation, using the existing method of pressure forming, applying a gradually increased pressure will realized the radial ring bodyware pressure forming. After the forming, a reverse magnetic field which has an opposite direction against the oriented magnetic field 6, and proper magnetic field strength, is needed to be introduced between the inner pole 1 and the outer pole 5 to demagnetize the bodyware. Then using the widely used sintering process and (or) heating treatment to process the radial ring bodyware to get the semifinished radial ring. After the finishing machining, a radial ring is produced. In this embodiment, the present invention only uses one set of outer pole 5 and magnetic conductive plate 4. It is optional to use more than one set. Additionally, the magnetic field introduced between the inner pole I and the outer pole 5 could be a permanent magnetic field, or a regularly changed magnetic field (such as pulse magnetic field), and also could be a irregularly changed magnetic field.

Referring the FIG. 2, after introducing the two poles (N and S) of a magnetic field generated by an electromagnet or a permanent magnet into the inner pole 1 and the outer pole 5 though a magnetic conductive component respectively, a strong magnetic field 6 will be formed between the inner pole 1 and the magnetic conductive plate 4 in the inside of the outer pole 5. If the mold cavity 2 is filled with magnetic powder, the magnetic powder in the magnetic field 6 will be sufficiently magnetized and oriented. If the first method is used, the nonmagnetic mold 3, mold cavity 2, and inner pole 1 are fixed on the platform of the apparatus and are relatively static. The magnetic conductive plate 4 is fixed on the on the outer pole 5, and the outer pole 5 is driven by a motor to rotate in high speed. If the second method is used, the outer pole 5 and the magnetic conductive plate 4 are fixed on the platform of the apparatus and are relatively static. The nonmagnetic mold 3, mold cavity 2, and inner pole 1 are connected with the rotation driver to rotate to magnetize and radially orient all the magnetic powder in the mold 5 cavity 2. At the same time of magnetization and orientation, using the existing method of pressure forming, applying a gradually increased pressure will realized the radial ring bodyware pressure forming. After the forming, a reverse magnetic field which has an opposite direction against the oriented magnetic field 6, and proper magnetic field strength, is needed to be introduced between the inner pole 1 and the outer pole 5 to demagnetize the bodyware. Then using the widely used sintering process and (or) heating treatment to process the radial ring bodyware to get the semifinished radial ring. After the finishing machining, a radial ring is produced. In this embodiment, the invention only uses one magnetic conductive plate 4. It is optional to use more than one magnetic conductive plate 4. Additionally, the magnetic field introduced between the inner pole 1 and the outer pole 5 could be a permanent magnetic field, or a regularly changed magnetic field (such as pulse magnetic field), and also could be a irregularly changed magnetic field.

Referring to FIG. 3, after introducing the two poles (N and S) of a magnetic field generated by an electromagnet or a permanent magnet into the first outer pole 7 and the second outer pole 8 though a magnetic conductive component respectively, two strong magnetic fields 6 will be formed between the magnetic conductive core 9 and the first outer pole 7, and between the magnetic conductive core 9and the second outer pole 8. If the mold cavity 2 is filled with magnetic powder, the magnetic powder in the magnetic field 6 will be sufficiently magnetized and oriented. If the first method is used, the nonmagnetic mold 3, the mold cavity 2, and magnetic conductive core 9 are fixed on the platform of the apparatus and are relatively static. The first outer pole 7 and the second outer pole 8 are connected with the rotation driver to rotate around the nonmagnetic mold 3, mold cavity 2, and magnetic conductive core 9. If the second method is used, the first outer pole 7 and the second outer pole 8 are fixed on the platform of the apparatus and are relatively static, nonmagnetic mold 3, mold cavity 2, and magnetic conductive core 9 are connected with the rotation driver to rotate to magnetize and radially orient all the magnetic powder in the mold cavity 2. At the same time of magnetization and orientation, using the existing method of pressure forming, applying a gradually increased pressure will realized the radial ring bodyware pressure forming. Then using the widely used sintering process and (or) heating treatment to process the radial ring bodyware to get the semifinished radial ring. After the finishing machining, a radial ring is produced. In this embodiment, the invention only uses one pair of outer poles (first outer pole 7 and the second outer pole 8). It is optional to use more than one pair of outer poles, or odd-numbered outer poles, for example, 3 outer poles, one N and two S. The magnetic field introduced between the first outer pole 7 and the second outer pole 8 could be a permanent magnetic field, or a regularly changed magnetic field (such as pulse magnetic field), and also could be a irregularly changed magnetic field.

In the embodiments 1 to 3, the present invention uses the method which is rotating and applying pressure at the same time to form the radial ring bodyware by pressure. Alternatively, the radial ring bodyware can also be formed using the steps of:

(a) applying a relatively small pressure onto the magnetic powder in the cavity of the mold to reduce the volume of the magnetic powder to 5% to 40%, the density of the powder is proper when the magnetic powder does not slide in the mold cavity obviously but can still rotate in the magnetic field;

(b) introducing magnetic field to the pole of the oriented magnetic field, rotating the magnetic powder in the mold relating for a plurality of rounds to the oriented magnetic field until the magnetic powder is totally magnetized;

(c) reducing the magnetic field strength of the oriented magnetic field until zero during rotating;

(d) applying more pressure on the magnetic powder until predetermined level; and

(e) applying reverse magnetic field to the radial ring bodyware for demagnetization, receiving radial ring bodyware.

The method and apparatus of the present invention can be used in producing sintering radial ring magnet, adhesion radial ring magnet, and injection radial ring magnet.

One skilled in the art will understand that the embodiment of the present invention as shown in the drawings and described above is exemplary only and not intended to be limiting.

It will thus be seen that the objects of the present invention have been fully and effectively accomplished. It embodiments have been shown and described for the purposes of illustrating the functional and structural principles of the present invention and is subject to change without departure from such principles. Therefore, this invention includes all modifications encompassed within the spirit and scope of the following claims. 

1. A method for forming radially oriented ring magnet, comprising the steps of: (a) positioning a magnetic powder in a ring mold cavity; and (b) radially orienting said magnetic powder in said ring mold cavity by a oriented magnetic field along radius or diameter direction, wherein said oriented magnetic field is distributed discretely 360° around said ring mold cavity, and during said forming process said oriented magnetic field and said magnetic powder have relative rotation.
 2. A method for forming radially oriented ring magnet, comprising the steps of: (a) applying a relatively small pressure onto a magnetic powder in a mold cavity to reduce the volume of said magnetic powder to 5% to 40%; (b) introducing a magnetic field to the poles of an oriented magnetic field, rotating said magnetic powder in said mold cavity relating to said oriented magnetic field until said magnetic powder is totally magnetized; (c) reducing the magnetic field strength of said oriented magnetic field until zero during rotating; (d) applying more pressure on said magnetic powder until a predetermined level; and (e) applying a reverse magnetic field to a radial ring bodyware for demagnetization, receiving said radial ring bodyware.
 3. An apparatus for forming radially oriented ring magnet, comprising a ring mold cavity in said oriented magnetic field, wherein said oriented is distributed discretely 360° around said ring mold cavity, and during said forming process said oriented magnetic field and said magnetic powder have relative rotation.
 4. The apparatus, as recited in claim 3, wherein said oriented magnetic field is a flake parallel magnetic field or a near parallel magnetic field.
 5. The apparatus, as recited in claim 4, wherein the width of said oriented magnetic field in the diameter direction is less than the inner diameter of said mold cavity.
 6. The apparatus, as recited in claim 5, wherein the width of said oriented magnetic field in the diameter direction is less than the one fifth of the inner diameter of said mold cavity.
 7. The apparatus, as recited in claim 6, wherein an inner pole of said oriented magnetic field is located in the center of said ring mold cavity, an outer pole of said oriented magnetic field is located in the outside of said ring mold cavity, wherein said apparatus comprises a magnetic conductive plate located inside said outer pole, and a strong magnetic field between said inner pole and said magnetic conductive plate.
 8. The apparatus, as recited in claim 7, wherein comprises more than one set of inner pole and magnetic conductive plate.
 9. The apparatus, as recited in claim 8, wherein said mold cavity and said inner pole of said oriented magnetic field are fixed, said outer pole of said oriented magnetic field and said magnetic conductive plate are connected with a rotation driver; or said outer pole and said magnetic conductive plate are fixed, said mold cavity and said inner pole are connected with said rotation driver.
 10. The apparatus, as recited in claim 6, wherein said first outer pole and said second outer pole of said oriented magnetic field are positioned at the outside of said ring mold cavity facing to each other, wherein said ring mold cavity further comprises a magnetic conductive core located at the center thereof, wherein said apparatus comprises two strong magnetic fields respectively between said magnetic conductive core and said first outer pole, and between said magnetic conductive core and said second outer pole.
 11. The apparatus, as recited in claim 10, wherein said mold cavity of said oriented magnetic field and said magnetic conductive core are fixed, said first outer pole and said second outer pole of said oriented magnetic field are connected with a rotation driver; or said first outer pole and said second outer pole of said oriented magnetic field are fixed, said mold cavity and said magnetic conductive core are connected with said rotation driver.
 12. The apparatus, as recited in claim 11, wherein said first outer pole and said second outer pole are more than one pair.
 13. The apparatus, as recited in claim 11, wherein said first outer pole and said second outer pole have an odd number. 